RESUMO
Bacterial chemotaxis is the directed movement of motile bacteria in gradients of chemoeffectors. This behavior is mediated by dedicated signal transduction pathways that couple environment sensing with changes in the direction of rotation of flagellar motors to ultimately affect the motility pattern. Azospirillum brasilense uses two distinct chemotaxis pathways, named Che1 and Che4, and four different response regulators (CheY1, CheY4, CheY6, and CheY7) to control the swimming pattern during chemotaxis. Each of the CheY homologs was shown to differentially affect the rotational bias of the polar flagellum and chemotaxis. The role, if any, of these CheY homologs in swarming, which depends on a distinct lateral flagella system or in attachment is not known. Here, we characterize CheY homologs' roles in swimming, swarming, and attachment to abiotic and biotic (wheat roots) surfaces and biofilm formation. We show that while strains lacking CheY1 and CheY6 are still able to navigate air gradients, strains lacking CheY4 and CheY7 are chemotaxis null. Expansion of swarming colonies in the presence of gradients requires chemotaxis. The induction of swarming depends on CheY4 and CheY7, but the cells' organization as dense clusters in productive swarms appear to depend on functional CheYs but not chemotaxis per se. Similarly, functional CheY homologs but not chemotaxis, contribute to attachment to both abiotic and root surfaces as well as to biofilm formation, although these effects are likely dependent on additional cell surface properties such as adhesiveness. Collectively, our data highlight distinct roles for multiple CheY homologs and for chemotaxis on swarming and attachment to surfaces.
RESUMO
The formation of biofilms on indwelling/implanted medical devices is a common problem. One of the approaches used to prevent biofilm formation on medical devices is to inhibit bacterial attachment by modification of the synthetic polymers used to fabricate the device. In this work, we assessed how micro-scale features (patterns) imprinted onto the surface of silicone elastomer similar to that used for medical applications influenced biofilm formation by Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. Patterns were transferred from a multi-patterned oxidized silicon-wafer master-template to silicone elastomer. Features consisted of bars, squares, and circles each extending 0.51 µm above the surface. Feature sizes ranged between 1.78 and 22.25 µm. Distances separating features ranged between 0.26 and 17.35 µm. Bacterial biofilm formation on discs cut from imprinted silicone elastomer was assessed by direct microscopic observation and quantified as the surface area covered by biofilm. Unpatterned silicone elastomer served as a control. Several of the micro-scale patterns imprinted into the silicone elastomer significantly reduced biofilm formation by each bacterium and interrupted biofilm continuity. Although there were differences in detail among strains, bacteria tended to attach in the area between features more than to the surface of the feature itself.
Assuntos
Animais , Biofilmes/crescimento & desenvolvimento , Biofilmes , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus epidermidis/crescimento & desenvolvimento , Staphylococcus epidermidis , Elastômeros de Silicone/isolamento & purificação , Elastômeros de Silicone/análise , Elastômeros de Silicone/efeitos adversos , Equipamentos e Provisões/microbiologiaRESUMO
We developed 15 novel polymorphic microsatellites for the Pacific oyster Crassostrea gigas by screening genes and expressed sequence tags (ESTs) found in GenBank. The number of alleles per locus ranged from two to 24 with an average of 8.7, and the values of observed heterozygosity (Ho) and expected heterozygosity (He) ranged from 0.026 to 0.750 and from 0.120 to 0.947, respectively. No significant pairwise linkage disequilibrium was detected among loci and eight loci conformed to Hardy-Weinberg equilibrium. Transferability of the markers was examined on five other Crassostrea species and all the markers were amplified successfully in at least one species. These new microsatellites should be useful for population genetics, parentage analysis and genome mapping studies of C. gigas and closely related species. The nine markers identified from known genes are expected to be especially valuable for comparative mapping as type I markers.